Hello guys:
     I have a problem in loading recommend model. I have 2 models, one is good(able to get recommend result) and another is not working. I checked these 2 models, both are  MatrixFactorizationModel object. But in the metadata, one is a PipelineModel and another is a MatrixFactorizationModel. Is below exception caused by this?

here are my stack trace:
Exception in thread "main" org.json4s.package$MappingException: Did not find value which can be converted into java.lang.String
        at org.json4s.reflect.package$.fail(package.scala:96)
        at org.json4s.Extraction$.convert(Extraction.scala:554)
        at org.json4s.Extraction$.extract(Extraction.scala:331)
        at org.json4s.Extraction$.extract(Extraction.scala:42)
        at org.json4s.ExtractableJsonAstNode.extract(ExtractableJsonAstNode.scala:21)
        at org.apache.spark.mllib.util.Loader$.loadMetadata(modelSaveLoad.scala:131)
        at org.apache.spark.mllib.recommendation.MatrixFactorizationModel$.load(MatrixFactorizationModel.scala:330)
        at org.brave.spark.ml.RecommandForMultiUsers$.main(RecommandForMultiUsers.scala:55)
        at org.brave.spark.ml.RecommandForMultiUsers.main(RecommandForMultiUsers.scala)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:497)
        at org.apache.spark.deploy.SparkSubmit$.org$apache$spark$deploy$SparkSubmit$$runMain(SparkSubmit.scala:731)
        at org.apache.spark.deploy.SparkSubmit$.doRunMain$1(SparkSubmit.scala:181)
        at org.apache.spark.deploy.SparkSubmit$.submit(SparkSubmit.scala:206)
        at org.apache.spark.deploy.SparkSubmit$.main(SparkSubmit.scala:121)
        at org.apache.spark.deploy.SparkSubmit.main(SparkSubmit.scala)

The attached files are my codes, FYI.
RecommandForMultiUsers.scala:55 is :
val model = MatrixFactorizationModel.load(sc, modelpath)


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Thanks&Best regards!
San.Luo